1. Field of the Invention
The present invention relates to a printed circuit board, and more particularly to a printed circuit board, which is adapted to increase the contact area between an IC and a printed circuit board, thus increasing the degree of adhesion therebetween.
2. Description of the Prior Art
These days, as the degree of integration of semiconductor devices is gradually increasing, the trend is for the number of connecting pads mounted on the semiconductor device, which are provided to connect the semiconductor device to exterior circuits, to increase, and also for the mounting density to increase.
In semiconductor equipment such as semiconductor packages, on which the above-mentioned semiconductor devices are mounted, in particular, portable information equipment such as notebook-sized personal computers, PDAs and cellular phones, demands for miniaturization and slimness and high connection reliability between the semiconductor devices and parent substrates are required so as to increase mounting density.
FIG. 1 is a cross-sectional view showing a structure of a substrate, which is useful for flip bonding of a conventional printed circuit board.
Referring to FIG. 1, in the manufacturing process of the conventional printed circuit board, a circuit pattern including a via land 102 is first formed on an insulation layer 100, and then a solder resist layer 104 is applied on the circuit pattern to cover the circuit pattern.
At this point, the outermost circuit pattern including the via land 102 is formed through electroless plating and electroplating processes.
The solder resist layer 104 is formed such that it allows a portion of the via land 102 to be exposed therethrough while covering the remaining area of the via land 102.
In other words, the solder resist layer 104 is formed on the insulation layer 100 in such a way that the solder resist layer covers the entire area of the circuit pattern, with the exception of the portion of the via land 102.
Then, a solder bump 106, which is to be connected to an IC (Integrated Circuit), is formed on the via land 102.
At this point, the solder p 106 is formed in such a way that conductive material such as conductive paste is printed on the via land 102 and is heat-treated, thus being deformed into a spherical shape, and the spherical mass is flattened through a coining process in order to compensate for mounting variation at the time of the IC mounting procedure.
The printed circuit board, which is manufactured through the above-described conventional technology, is a SOP (Solder On Pad) type.
However, since the conventional printed circuit board is manufactured in a manner such that the outermost circuit pattern including the via land 102 is formed through a plating process, the upper surface of the circuit pattern becomes uneven due to the plating tolerance. Consequently, in the case of formation of the solder bump 106, it is problematic in that there may be solder bumps 106 that are not connected to the IC at locations where printing material is insufficient.
Further, because the conventional printed circuit board is manufactured into an SOP type, the contact area between the IC bumps and the solder bumps of the printed circuit board is decreased, thus decreasing the reliability.